The coniferous Hemlock
trees commonly found in the northeastern United States today are not, in fact, the hemlock used as poison. That is
conium, a weed, and completely unrelated.
Of course, finding this out completely ruined so many jokes from elementary school. A hemlock tree grew just outside the fence to the playground and often we nerds would corner some unsuspecting stupid bully against the chain-link and threaten to make them eat hemlock.